1. Field of the Invention
The present invention relates to a radiating structure for a main spindle in a machining apparatus.
2. Description of the Related Art
Since a bearing or the like in a machine tool generates heat due to rotation of a main spindle to bring about thermal displacement or a rise in the pressure on a bearing and affect machining accuracy, a main spindle in a machining apparatus has a cooling structure in order to curb a rise in the temperature of the main spindle.
As a prior art technique pertaining to a cooling structure for a main spindle in a machining apparatus, for example, Japanese Patent Application Laid-Open No. 2014-062620 discloses a structure for a main spindle adopting lubrication of a bearing with air oil, in which air cooling a shaft and the bearing of the main spindle and air oil for lubrication are not mixed together.
Japanese Patent Application Laid-Open No. 2014-117119 discloses a structure which is provided with a cooling air passage along an axial center of a main spindle and includes a blowing section that sucks in outside air from a proximal end of the cooling air passage along with rotation of the main spindle and pressure-feeds the air in an axial center direction of the main spindle.
In a machining apparatus which performs machining with a tool mounted at a distal end of a main spindle, the main spindle distal end includes a drive key for preventing a phase shift in rotation direction between the main spindle and the tool. In connection with this, Japanese Patent Application Laid-Open No. 10-337625 discloses a structure in which drive keys are attached to a distal end of a main spindle by fixing a ring plate that is a ring-like member provided with the drive keys to the distal end of the main spindle, and a distal end portion of the main spindle does not enlarge by a centrifugal force due to absence of a key groove at the main spindle distal end portion.
The aforementioned technique disclosed in Japanese Patent Application Laid-Open No. 2014-062620 implements cooling of the shaft and the bearing as cooling targets by supplying air for cooling but suffers from the problem of the need for a complicated mechanism or complicated equipment.
The technique disclosed in Japanese Patent Application Laid-Open No. 2014-117119 implements cooling of a shaft and a bearing as cooling targets by providing the cooling air passage at the axial center and sucking in outside air from the blowing section provided at the proximal end of the cooling air passage along with rotation of the main spindle. In a machining apparatus, a mechanism for grasping a tool at a main spindle distal end is generally provided at an axial center, and application of the technique to the machining apparatus is difficult.